Kinematics of a major fan-like structure in the eastern part of the Sveconorwegian orogen, Baltic Shield, south-central Sweden

Wahlgren, Carl‐Henric; Cruden, Alexander; Stephens, Michael B.

doi:10.1016/0301-9268(94)90021-3

Cited by 116 publications

(50 citation statements)

References 39 publications

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“…A potential cause of these fracture systems may be the ca. 1.0 Ga deformation zone of the Sveconorwegian orogeny, which has recently been shown to extend into this area (Wahlgren et al 1994, Page et al 1996.…”

Section: Background Informationmentioning

confidence: 93%

FLUID INCLUSIONS IN LATE-STAGE Pb Mn As Sb MINERAL ASSEMBLAGES IN THE LANGBAN DEPOSIT, BERGSLAGEN, SWEDEN

Broman

2002

The Canadian Mineralogist

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The Långban deposit in the Paleoproterozoic Bergslagen ore province in southwestern central Sweden is well known for its complex and unique mineralogy. The largest number of exotic species occur in late-stage Pb-Mn-As-Sb-bearing fissures of disputed origin. Fluid inclusions in fissure-hosted allactite, barite, blixite, calcite, sarkinite, tilasite and finnemanite suggest a low-temperature near-surface formation at, or close to, atmospheric pressure, from aqueous NaCl-CaCl 2 -MgCl 2 solutions of initially moderate salinity. Mineral formation started at temperatures of ca. 180°C, with the fluid evolving through reactions with Mn-oxide-bearing dolomites and a sequence of boiling events, initiated by repeated fracturing, at temperatures fluctuating between ca. 80 and 130°C. This main stage is characterized by precipitation of alternating species (e.g., barite, calcite, allactite, native lead, pyrochroite), with solutions evolving further to heterogeneous high-salinity compositions at temperatures less than ca. 70°C. Late low-salinity inclusions formed through partial condensation of the expelled vapor phase. Continued formation of minerals (e.g., arsenites, H 2 O-rich arsenates) after the major boiling events is characterized by temperatures decreasing well below 70°C. The solutions responsible for the specific fissure-mineralization at Långban were introduced in a very shallow postSvecokarelian brittle tectonic environment, in conjunction with a ca. 1 Ga tectonothermal episode, or possibly coupled to post-1.8-Ga granitic magmatism. The absence of similar mineralized systems of brittle fissures on a regional scale suggests that the metals in the Långban fissures were derived very locally from the pre-existing volcanic-exhalative mineralization and not introduced from an external source.Keywords: Långban, ore deposit, fluid inclusions, allactite, barite, blixite, calcite, finnemanite, sarkinite, tilasite, Bergslagen, Sweden. SOMMAIRELe gisement de Långban, dans la province métallogénique paléoprotérozoïque de Bergslagen, dans le secteur sud-ouest central de la Suède, est reconnu pour ses assemblages complexes et uniques de minéraux. La majorité des espèces exotiques se trouvent dans les fissures tardives à Pb-Mn-As-Sb, d'origine controversée. Les inclusions fluides des minéraux déposés dans ces fissures, par exemple allactite, barite, blixite, calcite, sarkinite, tilasite et finnemanite, indiquent une faible température et une déposition à pression atmosphérique, ou presque, à partir de solutions contenant NaCl-CaCl 2 -MgCl 2 , de salinité intermédiaire, au moins au début. La formation de ces assemblages à débuté à environ 180°C, et les fluides ont évolué par réaction avec une séquence de dolomies manganifères et une série d'événements d'ébullition initiés par ouverture répétée de fractures à une température fluctuant entre 80 et 130°C. L'étape principale est marquée par la précipitation d'une alternance d'espèces (e.g., barite, calcite, allactite, plomb natif, pyrochroïte), et par l'évolution progressive des...

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Section: Background Informationmentioning

confidence: 93%

FLUID INCLUSIONS IN LATE-STAGE Pb Mn As Sb MINERAL ASSEMBLAGES IN THE LANGBAN DEPOSIT, BERGSLAGEN, SWEDEN

Broman

2002

The Canadian Mineralogist

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“…1c, d). In the frontal wedge, the bedrock is non-penetratively deformed and exhibits a fan structure across strike (Wahlgren et al, 1994). Sveconorwegian metamorphism grades from greenschist-facies in the east to amphibolite-facies in the west.…”

Section: The Eastern Segmentmentioning

confidence: 99%

“…Later, Viola et al (2011) outlined a similar core complex model integrating also the down-dip westvergent shear structures along the southern Mylonite Zone. A contrasting, transpressional, tectonic model has been proposed by Wahlgren et al (1994), based on the fan-like geometry of structures at the Sveconorwegian Front (transitional section-frontal wedge, Fig. 1c-d).…”

Section: Exhumation and P-t-t-d Evolutionmentioning

confidence: 99%

Exhumation of an eclogite terrane as a hot migmatitic nappe, Sveconorwegian orogen

Möller

Andersson

Dyck

et al. 2015

Lithos

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We demonstrate a case of eclogite exhumation in a partially molten, low-viscosity fold nappe within high-grade metamorphosed crust in the Eastern Segment of the Sveconorwegian orogen. The nappe formed during tectonic extrusion, melt-weakening assisted exhumation and foreland-directed translation of eclogitized crust, and stalled at 35-40 km depth within the collisional belt. The eclogites are structurally restricted to a regional recumbent fold in which stromatic orthogneiss with pods of amphibolitized eclogite make up the core. Hightemperature mylonitic gneiss with remnants of kyanite eclogite (P N 15 kbar) composes a basal shear zone 50 km long and b 4 km wide. Heterogeneously sheared and partly migmatized augen gneiss forms a tectonostratigraphic marker in front of and beneath the nappe, and is in turn structurally enveloped by a composite sequence of orthogneisses and metabasites. The entire tectonostratigraphic pile underwent near-pervasive deformation and recrystallization under high-pressure granulite and upper amphibolite conditions. U-Pb SIMS metamorphic zircon ages of eclogite and stromatic orthogneiss constrain the time of eclogitization at 988 ± 6 Ma and 978 ± 7 Ma. Migmatization, concomitant deformation, and exhumation are dated at 976 ± 6 Ma, and crystallization of post-kinematic melt at 956 ± 7 Ma. Orthogneiss protoliths are dated at 1733 ± 11 and 1677 ± 10 Ma (stromatic gneiss) and 1388 ± 7 Ma (augen gneiss in footwall), demonstrating origins indigenous to the Eastern Segment. Eclogitization and exhumation were coeval with the Rigolet phase of the Grenvillian orogeny, reflecting the late stage of continental collision during construction of the supercontinent Rodinia.

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“…In the east, the upper tectonic level is characterised by nonpenetrative ductile deformation and greenschist to amphibolite facies metamorphism (Wahlgren et al, 1994). The upper level contains 1.81-1.77 Ga and 1.74-1.66 Ga granite to syenite plutonic rocks intruded in the southern parts by 1.47-1.38 Ga Hallandian plutons (Johansson et al, 1993;Brander et al, 2012) and 1.28-1.22 Ga plutons (Hansen and Lindh, 1991;Berglund, 1997;Söderlund and Ask, 2006;Jarl, 2002).…”

Section: Eastern Segmentmentioning

confidence: 97%

“…It is limited in the east by the Sveconorwegian Frontal Deformation Zone (Wahlgren et al, 1994). The easternmost lithotectonic domain of the orogen, called the Eastern Segment, is interpreted as a parautochthonous domain attached to Fennoscandia before the Sveconorwegian Orogeny .…”

Section: Eastern Segmentmentioning

confidence: 99%

Mesoproterozoic continental growth: U–Pb–Hf–O zircon record in the Idefjorden Terrane, Sveconorwegian Orogen

Petersson

Scherstén

Bingen

et al. 2015

Precambrian Research

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Kinematics of a major fan-like structure in the eastern part of the Sveconorwegian orogen, Baltic Shield, south-central Sweden

Cited by 116 publications

References 39 publications

FLUID INCLUSIONS IN LATE-STAGE Pb Mn As Sb MINERAL ASSEMBLAGES IN THE LANGBAN DEPOSIT, BERGSLAGEN, SWEDEN

FLUID INCLUSIONS IN LATE-STAGE Pb Mn As Sb MINERAL ASSEMBLAGES IN THE LANGBAN DEPOSIT, BERGSLAGEN, SWEDEN

Exhumation of an eclogite terrane as a hot migmatitic nappe, Sveconorwegian orogen

Mesoproterozoic continental growth: U–Pb–Hf–O zircon record in the Idefjorden Terrane, Sveconorwegian Orogen

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